Magnetic core and method of making the same



Aug. 9, 1932.

MAGNETIC CORE ANI'j METHD oF MAKING THE sAME` Filed sept. 1o, 1930 I l I I A l .0,000 /00,000 /54000 200,0@ 250,0W 300,000

fname/mr i yPatented 'Augu 9, 1932 AUNITED STATES PATENT owl-FICE i RANDALL GILLIS, OF LAXGBANGE, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COM- YPANY, INCORPORATED,'OF NEW YORK, N. Y., A CORPORATION OF NEW YORK MAGNETIC CORE AND METHOD OF MAKING THE'SAME Application led September 10, 1930. Serial No. 480,880.

This .invention relates to'magnetic cores andrmethods of making the same, and more to J. W. Andrews et al., wherein iinely divided particles of a magnetic material such as an alloy of nickeland iron are Coated with au insulating material, and are then compressed into cores ofthe desired shape and size, which are heat treated to impart the desired electrical and magnetic properties thereto.-

Objects of the invention are to provide cores having improved magnetic characteristics and lower hysteresis losses, and to provide an improved method of making such cores.

In accordance with one embodiment of the invention, a pressure materially higher than those heretofore used is employed in compressing the material into cores, and the cores are then subjected to an annealing treatment tobring 'about the optimum of'mechanical, electrical, and magnetic properties in the tinished cores.

The invention will be'clearly understood from the following detailed desoriptionof one embodiment thereof, taken in connection with the accompanying drawing, in which Fig. 1 is a graphical illustration showing the relation between the forming pressure and the hysteresis loss inmagnetic cores; lF i 2 is a similar illustration showing the relation between the forming pressure and the permeability in magnetic cores, and

Fig. 3 is a perspective view of a section of a. loading coil core made in accordance with the present invention.-

In carrying out the present invention the magnetic material employed is preferably prepared from a nickel-iron alloy known as permalloy, a ratio of 81 parts'nickel to 19 parts iron being satisfactory for most purposes. The alloy is treated in the manner disclosed in Patent 1,669,649, issued May 15, 1928 to C. P. Beath et al. toreduce it to a finely divided form, the particles being preferably of such neness that they will pass a 120-mesh screen or finer. The alloy particles are then annealed in the known manner, after which they are coated with an insulating material which insulates the particles from each other .and which may be of the composition described in the J. W. Andrews et al, patents referred to above. pressed into cores or rings under sufficient pressure to create an autogenous bond between the insulated particles of metal which holds them together in rigid relation to each other. v

`In forming the mass into cores, it has been found that a pressure substantially in excess of 200,000 pounds per squareinch is dcsirable in that the hy'fsteresis loss in cores The mass is then dried and,

formed at such higher pressures is reduced.

This may be seen from an examination of Fig. l1, wherein the abscissze represent forming pressures inpounds per square inch and the ordinates represent hysteresis loss in watts per cycle per cm3 1010. From the values shown iii-Fig. land from further experiments it has been determined that -a forming pressure of about 250,000 pounds per square inch or. higher is'especially suitable. hysteresis loss of permalloy and other magnetic metals was thought to be increased by cold working but as evidenced by the curve in Fig. l a lower hysteresis loss is obtained by using higher forming pressures. It is believed that the decrease in hysteresis loss with increased forming pressure is due to the magnetic flux being more uniformly distributed throughout the cross-section of the core beity of the cores increases with increased form,- 10

The

y absclss represent forming pressure and the' 7cycle per cmsXlOl".

ing pressure, as shown inFig. 2, wherein the ordinates represent permeability in watts per It will e seen from an, examination of Fig. 2 that the permeability increases slowly but yet appreciably as the forming pressure is increased above 200,000 ounds per square inch. In other words, t e roperty of permeability is not adversely a ected by the higher pressures, but

on the contrary tends to slightly higher values.

-After the cores have been compressed as above described, they may be annealed in the,

known manner to impart the desired electrical and mechanical properties thereto, after which they are ready to receive the usual toroidal winding preparatory to being placed in a telephone system.

While the invention has been described in connection with a composition having certain specified ingredients, it is applicable tog differently constituted compositions, and the details hereinabove set forth may be considerably varied without departing from the scope of the invention.

What is claimed is:

' 1. A mafrnetic core composed of insulated articles o? a nickel-iron alloy held together y anautogenous bond formed under a pressure of about 250,000 pounds per square inch.

2. A. method of forming magnetic cores from insulated particles of a nickel-iron alloy, which consists in compressing the particles into the desired form under a pressure of about 250,000 pounds per square inch.

3. A m/ethod of forming magnetic cores from particles of a nickel-iron alloy, which consists in coating said particles with an insulating composition, compressing the insulated particles into a core under a pressure of y at least 250,000 pounds per square inch, and

annealing the formed cores. In witness whereof, I hereunto subscribe my name this 29th day of August A. D.,

RANDALL GILLIS. 

